A submicron broadband surface-plasmon-polariton unidirectional coupler

Abstract

The manipulation of light propagation is a basic subject in optics and has many important applications. With the development of nano-optics, this area has been downscaled to wavelength or even subwavelength scales. One of the most efficient ways to control light propagation is to exploit interference effects. Here, by manipulating the interference between two nanogrooves on a metal surface, we realize a submicron broadband surface-plasmon-polariton (SPP) unidirectional coupler. More importantly, we find an anomalous bandwidth shrinking behavior in the proposed SPP unidirectional coupler as the groove separation is down to a subwavelength scale of one-quarter of the SPP wavelength. This abnormal behavior is well explained by considering the contribution of the near-field quasi-cylindrical waves in addition to the interference of propagating SPPs and the dispersion effects of individual grooves. Such near-field effects provide new opportunities for the design of ultracompact optical devices.

Tunable Unidirectional Coupling of Surface Plasmon Polaritons Utilizing a V-Shaped Slot Nanoantenna Column

“…Traditional SPP coupler, such as prisms and gratings, are bulky for high density integration. In recent years, numbers of methods for directional coupling of SPP using nanostructures and nanoantennas have been proposed and demonstrated, including the use of complex slits [5,6], two nanostructures or nanoantennas nearby [7][8][9], aperiodic metallic groove arrays [10], and oblique incidence on symmetrical nanostructures [11,12]. However, in most of these methods, SPP are coupled and propagate in a fixed direction, which are determined by the structures or the incident conditions.…”

Ultra-broadband unidirectional launching of surface plasmon polaritons by a double-slit structure beyond the diffraction limit

“…By adopting the chirped plasmonic gratings with a lateral dimension of about 17 μm 23 or 4 μm, 24 the bandwidths of the unidirectional SPP source reached 190 nm 23 and 210 nm. 24 With a pair of phased nanoslits, 25 the broadband unidirectional SPPs with a bandwidth of about 300 nm were numerically predicted, while the generated SPPs from all of these SPP launchers propagated bulkily along the metal surface, [3][4][5][6][7][8][9][10][12][13][14][15][16][17][18][19][20][21][22][23][24][25] leading to diverging SPP sources or approximate plane-wave SPP sources on the metal surface.…”

“…Although some of these unidirectional SPP launchers possessed very small lateral dimensions ( parallel to the SPP propagation direction along the metal surface), which can even be downscaled to subwavelength, [12][13][14]22,23 nearly all of the unidirectional SPP launchers had very large longitudinal dimensions (>10λ, perpendicular to the SPP propagation direction along the metal surface). [3][4][5][6][7][8][9][12][13][14][15][16][17][18][19][20][21][22][23][24][25] This significantly limits the on-chip integration density of the plasmonic devices. Moreover, the generated SPPs propagated bulkily along the metal surface without any confinements.…”

“…Moreover, the generated SPPs propagated bulkily along the metal surface without any confinements. [3][4][5][6][7][8][9][10][12][13][14][15][16][17][18][19][20][21][22][23][24][25] This makes it hard to directly couple the generated SPPs to subwavelength plasmonic waveguides. What is worse, the bulky propagation of the SPPs would bring large crosstalk between different plasmonic devices in high-integration plasmonic circuits.…”

Light manipulation with encoded plasmonic nanostructures

“…Unidirectional SPP excitation from either side of the slit can be switched by varying the real part of the polymer permittivity with a pump laser beam as shown in Figure 4c. Gong's group also reported unidirectional SPP excitation from two grooves with different depth [51]. The aforementioned structures are normally illuminated with linear polarized light.…”